Shop ventilation question

[Peter Franklin]

Hi,

I'm about to start conversion of a garage into a woodshop to include a 20x20 room for machines that's sound proofed with no windows to limit sound travel and one door that will join to a 10x20 bench room that's not sound proofed but insulated and somewhat air tight to save costs on hvac and with 2 windows and an exterior door.

When I'm not working on machines I'll have the door open to the bench room but it dawned on me that I might want to have some kind of ventilation for times when the door is closed and I'm running the machines. Maybe one vent to bring air in and one to push it out? It would be tricky to build a vent that is also sound proofed but not impossible (especially considering all the sound proofing I'm already doing). I'd avoid venting to the outside so I don't lose conditioned air, but I could put one vent into the bench room and another into the main house.

But I also wonder if it's worth the fuss. I suspect the longest stretch I'd go holed up in the machine room with the door closed is a couple hours, but probably not that often. Contractor who's helping me hasn't raised any code issues, so I'm guessing I don't have to.

Any thoughts on this? Am I missing something obvious? I'll be using mini splits for hvac (I'm told ducted vs ductless so I can have a filter for wood dust). No other hvac tied from house. No heavy use of finishing or chemicals - just occasional.

?

Thanks!

[Brian Gouldman]

I have a Panasonic FV-04VE1 single room ERV that I plan to put in my shop for air exchange. I extensively air barriered my detached shop with Prosoco products and wanted something that could do controlled air exchange so there wasn’t stale air if I wasn’t able to be in the shop for weeks at a time. Similarly, if I was doing something that made undesirable smells (soldering, etc…) I could get fresh air into the shop while keeping the incoming air as conditioned as possible.

I haven’t installed it yet so I can’t give a first hand review, but by and large it’s a positively reviewed ERV and about the only option you have for a small space. It has multiple speeds and can be wired up to switches so you can adjust air volume as needed on demand.

[Peter Franklin]

Interesting. I just read the description that says he pulls air from outdoors. Any issues with the fact it's pulling in unconditioned air during cold winters or humid summers? Or is it not powerful enough to make a difference?

[Brian Gouldman]

Since it’s an ERV, it exchanges temperature and moisture between the air streams. Probably not quite a perfect equilibrium, but some amount of exchange occurs. In the summer I expect my conditioned air will dry out the incoming air some. In the winter, well the humidity just drops out completely except on days it is warm enough to rain. When the humidity spikes on those days the shop still stays below 40% RH. I assume because the shop itself is so dried out it is absorbing the moisture in the air.

For humidity in the summer, mid-Atlantic, I have a stand-alone wall mounted dehumidifier set at 45-50%. It is working amazingly for its first summer. That I got from Innovative Dehumidifiers. I got it because I found the mini split dry mode to be completely inadequate. All it did for me was drop the temp way lower than I wanted and drive up the RH to an uncomfortable level. Now with the dehumidifier, it cycles on once every couple hours for a few minutes and easily keeps the RH at set point. The minisplit cuts on around the same time, largely to combat the heat the dehumidifier puts out and then shuts off.

[Cameron Wood]

Maybe I'm missing something, but why would you vent the dusty noisy workshop to the house?

[Peter Franklin]

I have 4 walls, 2 abut the outside, which I think I want to avoid so I don't have to deal with unconditioned air. That leaves the other 2 walls - one which joins the bench room and another the house. If I were to split the air handling up, I could pull air from the house into the machine room and push air from the machine room into the bench room. I'd create soundproof ducts so noise wouldn't be an issue, but I might need to deal with whatever is going into the benchroom, which I don't think would be much.

[Thomas Crawford]

Are you worried about noise transmission to the house or to outside? If you are worried about outside you are probably overthinking it, even if you had several windows.

[Paul F Franklin]

It would definitely be a code violation to vent a *garage* to the house, but since you are permanently(?) converting the space to a shop I imagine it might be allowed. IIWM, I'd avoid it just for dust reasons. But even there, it's no worse than all of us that have basement shops. An ERV as Brian suggests would be a good way to bring in fresh air while minimizing the loss of conditioned air. But I think most ERVs have a network of tiny passages in their exchangers, so keeping it clean might be a challenge in a shop.

One thing you want to consider is the heat generated by the machines. In my 900+ sq foot basement shop, running the dust collector and the jointer/planer or table saw for a couple of hours noticeably warms the shop. It's roughly equivalent to running a 5000 watt electric heater. So you'll want to plan for the heat load when sizing your mini-split. A filtered exchange of air between the machine room and other shop area will help even the temperature and would provide a good opportunity to add air cleaning filtration at the same time. Of course for that, you'd need two openings between the spaces.

[Bill Dufour]

Climate? Any building codes about ventilation and emergency exits in you country? In the USA school science labs have to have two exit doors in case of fire. I beelive bedroom sahve to have a door and either another door or big window for exits.
Bill D

USA